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Pantazopoulou M, Lamprokostopoulou A, Karampela DS, Alexaki A, Delis A, Coens A, Samiotaki M, Kriebardis AG, Melki R, Pagakis SN, Stefanis L, Vekrellis K. Differential intracellular trafficking of extracellular vesicles in microglia and astrocytes. Cell Mol Life Sci 2023; 80:193. [PMID: 37391572 DOI: 10.1007/s00018-023-04841-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Revised: 06/07/2023] [Accepted: 06/15/2023] [Indexed: 07/02/2023]
Abstract
Extracellular vesicles (EVs) have emerged as key players in cell-to-cell communication in both physiological and pathological processes in the Central Nervous System. Thus far, the intracellular pathways involved in uptake and trafficking of EVs within different cell types of the brain are poorly understood. In our study, the endocytic processes and subcellular sorting of EVs were investigated in primary glial cells, particularly linked with the EV-associated α-synuclein (α-syn) transmission. Mouse microglia and astrocytic primary cultures were incubated with DiI-stained mouse brain-derived EVs. The internalization and trafficking pathways were analyzed in cells treated with pharmacological reagents that block the major endocytic pathways. Brain-derived EVs were internalized by both glial cell types; however, uptake was more efficient in microglia than in astrocytes. Colocalization of EVs with early and late endocytic markers (Rab5, Lamp1) indicated that EVs are sorted to endo-lysosomes for subsequent processing. Blocking actin-dependent phagocytosis and/or macropinocytosis with Cytochalasin D or EIPA inhibited EV entry into glial cells, whereas treatment with inhibitors that strip cholesterol off the plasma membrane, induced uptake, however differentially altered endosomal sorting. EV-associated fibrillar α-Syn was efficiently internalized and detected in Rab5- and Lamp1-positive compartments within microglia. Our study strongly suggests that EVs enter glial cells through phagocytosis and/or macropinocytosis and are sorted to endo-lysosomes for subsequent processing. Further, brain-derived EVs serve as scavengers and mediate cell-to-glia transfer of pathological α-Syn which is also targeted to the endolysosomal pathway, suggesting a beneficial role in microglia-mediated clearance of toxic protein aggregates, present in numerous neurodegenerative diseases.
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Affiliation(s)
- Marina Pantazopoulou
- Biomedical Research Foundation Academy of Athens-BRFAA, Clinical-Experimental Surgery & Translational Research, 4, Soranou Tou Efesiou Street, 11527, Athens, Greece.
| | | | | | - Anastasia Alexaki
- Biomedical Research Foundation Academy of Athens-BRFAA, Centre of Basic Research, Athens, Greece
| | - Anastasios Delis
- Biomedical Research Foundation Academy of Athens-BRFAA, Centre of Basic Research, Athens, Greece
| | - Audrey Coens
- Institut Francois Jacob (MIRCen), CEA and Laboratory of Neurodegenerative Diseases, CNRS, Fontenay-Aux-Roses Cedex, France
| | - Martina Samiotaki
- Institute for Bioinnovation, Biomedical Sciences Research Center 'Alexander Fleming', Fleming 34, 16672, Vari, Greece
| | - Anastasios G Kriebardis
- Laboratory of Reliability and Quality Control in Laboratory Hematology (HemQcR), Department of Biomedical Sciences, School of Health & Welfare Sciences, University of West Attica (UniWA), Egaleo, Greece
| | - Ronald Melki
- Institut Francois Jacob (MIRCen), CEA and Laboratory of Neurodegenerative Diseases, CNRS, Fontenay-Aux-Roses Cedex, France
| | - Stamatis N Pagakis
- Biomedical Research Foundation Academy of Athens-BRFAA, Centre of Basic Research, Athens, Greece
| | - Leonidas Stefanis
- Biomedical Research Foundation Academy of Athens-BRFAA, Clinical-Experimental Surgery & Translational Research, 4, Soranou Tou Efesiou Street, 11527, Athens, Greece
| | - Kostas Vekrellis
- Biomedical Research Foundation Academy of Athens-BRFAA, Centre of Basic Research, Athens, Greece
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2
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Pateras IS, Williams C, Gianniou DD, Margetis AT, Avgeris M, Rousakis P, Legaki AI, Mirtschink P, Zhang W, Panoutsopoulou K, Delis AD, Pagakis SN, Tang W, Ambs S, Warpman Berglund U, Helleday T, Varvarigou A, Chatzigeorgiou A, Nordström A, Tsitsilonis OE, Trougakos IP, Gilthorpe JD, Frisan T. Short term starvation potentiates the efficacy of chemotherapy in triple negative breast cancer via metabolic reprogramming. J Transl Med 2023; 21:169. [PMID: 36869333 PMCID: PMC9983166 DOI: 10.1186/s12967-023-03935-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Accepted: 01/27/2023] [Indexed: 03/05/2023] Open
Abstract
BACKGROUND Chemotherapy (CT) is central to the treatment of triple negative breast cancer (TNBC), but drug toxicity and resistance place strong restrictions on treatment regimes. Fasting sensitizes cancer cells to a range of chemotherapeutic agents and also ameliorates CT-associated adverse effects. However, the molecular mechanism(s) by which fasting, or short-term starvation (STS), improves the efficacy of CT is poorly characterized. METHODS The differential responses of breast cancer or near normal cell lines to combined STS and CT were assessed by cellular viability and integrity assays (Hoechst and PI staining, MTT or H2DCFDA staining, immunofluorescence), metabolic profiling (Seahorse analysis, metabolomics), gene expression (quantitative real-time PCR) and iRNA-mediated silencing. The clinical significance of the in vitro data was evaluated by bioinformatical integration of transcriptomic data from patient data bases: The Cancer Genome Atlas (TCGA), European Genome-phenome Archive (EGA), Gene Expression Omnibus (GEO) and a TNBC cohort. We further examined the translatability of our findings in vivo by establishing a murine syngeneic orthotopic mammary tumor-bearing model. RESULTS We provide mechanistic insights into how preconditioning with STS enhances the susceptibility of breast cancer cells to CT. We showed that combined STS and CT enhanced cell death and increased reactive oxygen species (ROS) levels, in association with higher levels of DNA damage and decreased mRNA levels for the NRF2 targets genes NQO1 and TXNRD1 in TNBC cells compared to near normal cells. ROS enhancement was associated with compromised mitochondrial respiration and changes in the metabolic profile, which have a significant clinical prognostic and predictive value. Furthermore, we validate the safety and efficacy of combined periodic hypocaloric diet and CT in a TNBC mouse model. CONCLUSIONS Our in vitro, in vivo and clinical findings provide a robust rationale for clinical trials on the therapeutic benefit of short-term caloric restriction as an adjuvant to CT in triple breast cancer treatment.
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Affiliation(s)
- Ioannis S Pateras
- 2nd Department of Pathology, "Attikon" University Hospital, Medical School, National and Kapodistrian University of Athens, 124 62, Athens, Greece.
| | - Chloe Williams
- Department of Integrative Medical Biology, Umeå University, 901 87, Umeå, Sweden
| | - Despoina D Gianniou
- Department of Cell Biology and Biophysics, Faculty of Biology, National and Kapodistrian University of Athens, 157 84, Athens, Greece
| | - Aggelos T Margetis
- 2nd Department of Internal Medicine, Athens Naval and Veterans Hospital, 115 21, Athens, Greece
| | - Margaritis Avgeris
- Laboratory of Clinical Biochemistry-Molecular Diagnostics, Second Department of Pediatrics, School of Medicine, National and Kapodistrian University of Athens, "P. & A. Kyriakou" Children's Hospital, 115 27, Athens, Greece.,Department of Biochemistry and Molecular Biology, Faculty of Biology, National and Kapodistrian University of Athens, 157 71, Athens, Greece
| | - Pantelis Rousakis
- Department of Biology, School of Science, National and Kapodistrian University of Athens, 157 84, Athens, Greece
| | - Aigli-Ioanna Legaki
- Department of Physiology, Medical School, National and Kapodistrian University of Athens, 115 27, Athens, Greece
| | - Peter Mirtschink
- Institute for Clinical Chemistry and Laboratory Medicine, University Hospital and Faculty of Medicine, Technische Universität Dresden, 013 07, Dresden, Germany
| | - Wei Zhang
- Swedish Metabolomics Centre, Department of Plant Physiology, Umeå University, 901 87, Umeå, Sweden
| | - Konstantina Panoutsopoulou
- Department of Biochemistry and Molecular Biology, Faculty of Biology, National and Kapodistrian University of Athens, 157 71, Athens, Greece
| | - Anastasios D Delis
- Centre for Basic Research, Bioimaging Unit, Biomedical Research Foundation, Academy of Athens, 115 27, Athens, Greece
| | - Stamatis N Pagakis
- Centre for Basic Research, Bioimaging Unit, Biomedical Research Foundation, Academy of Athens, 115 27, Athens, Greece
| | - Wei Tang
- Molecular Epidemiology Section, Laboratory of Human Carcinogenesis, Center for Cancer Research (CCR), NCI, NIH, Bethesda, MD, 20892-4258, USA.,Data Science & Artificial Intelligence, R&D, AstraZeneca, Gaithersburg, MD, USA
| | - Stefan Ambs
- Molecular Epidemiology Section, Laboratory of Human Carcinogenesis, Center for Cancer Research (CCR), NCI, NIH, Bethesda, MD, 20892-4258, USA
| | - Ulrika Warpman Berglund
- Science for Life Laboratory, Department of Oncology-Pathology, Karolinska Institutet, 171 76, Stockholm, Sweden
| | - Thomas Helleday
- Science for Life Laboratory, Department of Oncology-Pathology, Karolinska Institutet, 171 76, Stockholm, Sweden.,Weston Park Cancer Centre, Department of Oncology and Metabolism, University of Sheffield, Sheffield, S10 2RX, UK
| | - Anastasia Varvarigou
- Department of Paediatrics, University of Patras Medical School, General University Hospital, 265 04, Patras, Greece
| | - Antonios Chatzigeorgiou
- Department of Physiology, Medical School, National and Kapodistrian University of Athens, 115 27, Athens, Greece.,Institute for Clinical Chemistry and Laboratory Medicine, University Hospital and Faculty of Medicine, Technische Universität Dresden, 013 07, Dresden, Germany
| | - Anders Nordström
- Swedish Metabolomics Centre, Department of Plant Physiology, Umeå University, 901 87, Umeå, Sweden
| | - Ourania E Tsitsilonis
- Department of Biology, School of Science, National and Kapodistrian University of Athens, 157 84, Athens, Greece
| | - Ioannis P Trougakos
- Department of Cell Biology and Biophysics, Faculty of Biology, National and Kapodistrian University of Athens, 157 84, Athens, Greece
| | - Jonathan D Gilthorpe
- Department of Integrative Medical Biology, Umeå University, 901 87, Umeå, Sweden
| | - Teresa Frisan
- Department of Molecular Biology and Umeå Centre for Microbial Research (UCMR), Umeå University, 901 87, Umeå, Sweden.
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3
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Daskalakis K, Alexandraki KI, Kloukina I, Kassi E, Felekouras E, Xingi E, Pagakis SN, Tsolakis AV, Andreakos E, Kaltsas G, Kambas K. Increased autophagy/mitophagy levels in primary tumours of patients with pancreatic neuroendocrine neoplasms. Endocrine 2020; 68:438-447. [PMID: 32114655 PMCID: PMC7266843 DOI: 10.1007/s12020-020-02228-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/16/2019] [Accepted: 02/11/2020] [Indexed: 12/24/2022]
Abstract
BACKGROUND/AIMS We assessed the levels of autophagy and mitophagy, that are linked to cancer development and drug resistance, in well differentiated pancreatic neuroendocrine neoplasms (PanNENs) and correlated them with clinico-pathological parameters. METHODS Fluorescent immunostaining for the autophagy markers LC3Β and p62/or LAMP1 was performed on 22 PanNENs and 11 controls of normal pancreatic tissues and validated through Western blotting. Autophagy quantitative scoring was generated for LC3B-positive puncta and analysed in relation to clinico-pathological parameters. TOMM20/LC3B qualitative assessment of mitophagy levels was undertaken by fluorescent immunostaining. The presence of autophagy/mitophagy was validated by transmission electron microscopy. RESULTS Autophagy levels (LC3B-positive puncta/cell) were discriminative for normal vs. NEN pancreatic tissue (p = 0.007). A significant association was observed between autophagy levels and tumour grade (Ki67 < 3% vs. Ki67 ≥ 3%; p = 0.021), but not functionality (p = 0.266) size (cut-off of 20 mm; p = 0.808), local invasion (p = 0.481), lymph node- (p = 0.849) and distant metastases (p = 0.699). Qualitative assessment of TOMM20/LC3B demonstrated strong mitophagy levels in PanNENs by fluorescent immunostaining as compared with normal tissue. Transmission electron microscopy revealed enhanced autophagy and mitophagy in PanNEN tissue. Response to molecular targeted therapies in metastatic cases (n = 4) did not reveal any patterns of association to autophagy levels. CONCLUSIONS Increased autophagy levels are present in primary tumours of patients with PanNENs and are partially attributed to upregulated mitophagy. Grade was the only clinico-pathological parameter associated with autophagy scores.
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Affiliation(s)
- Kosmas Daskalakis
- 1st Department of Propaupedic Internal Medicine, Endocrine Oncology Unit, Laiko Hospital, National and Kapodistrian University of Athens, Athens, Greece.
- Department of Surgery, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
| | - Krystallenia I Alexandraki
- 1st Department of Propaupedic Internal Medicine, Endocrine Oncology Unit, Laiko Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Ismini Kloukina
- Center of Basic Research, Biomedical Research Foundation of the Academy of Athens, Athens, Greece
| | - Evanthia Kassi
- 1st Department of Propaupedic Internal Medicine, Endocrine Oncology Unit, Laiko Hospital, National and Kapodistrian University of Athens, Athens, Greece
- Department of Biological Chemistry, Medical School, National and Kapodistrian University of Athens, Athens, Greece
| | - Evangelos Felekouras
- First Department of Surgery, Laikon General Hospital, University of Athens Medical School, Athens, Greece
| | - Evangelia Xingi
- Microscopy Unit, Hellenic Pasteur Institute, Vas. Sofias 127, Athens, 11521, Greece
| | - Stamatis N Pagakis
- Biological Imaging Unit, Biomedical Research Foundation of the Academy of Athens, Athens, 11527, Greece
| | - Apostolos V Tsolakis
- Department of Oncology and Pathology, Karolinska Institute, Solna R8:04, Stockholm, 17177, Sweden
| | - Evangelos Andreakos
- Laboratory of Immunobiology, Center for Clinical, Experimental Surgery and Translational Research, Biomedical Research Foundation of the Academy of Athens, 11527, Athens, Greece
| | - Gregory Kaltsas
- 1st Department of Propaupedic Internal Medicine, Endocrine Oncology Unit, Laiko Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Konstantinos Kambas
- Laboratory of Molecular Genetics, Department of Immunology, Hellenic Pasteur Institute, Athens, Greece
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Papadopoulou EL, Samara A, Barberoglou M, Manousaki A, Pagakis SN, Anastasiadou E, Fotakis C, Stratakis E. Silicon scaffolds promoting three-dimensional neuronal web of cytoplasmic processes. Tissue Eng Part C Methods 2010; 16:497-502. [PMID: 19686056 DOI: 10.1089/ten.tec.2009.0216] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Primary neurons were grown on structured silicon (Si) substrates, in the absence of chemotropic factors or synthetic extracellular matrix. The Si substrates used for the study comprise hierarchical structures in the micro- and nanolength scales. The substrates were structured via femtosecond laser irradiation of the Si wafer, in a reactive SF(6) environment. Electron microscopy revealed that the neurons formed an elaborate web of cytoplasmic processes in the absence of glial elements. The neuronal cytoplasm autografted the depth of the spikes, and the neurite sprouting took place over the spikes surface. Here we demonstrate how microfabrication of a Si surface provides an excellent platform for multifaceted studies of neuronal specimens.
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Affiliation(s)
- Evie L Papadopoulou
- Foundation for Research and Technology-Hellas, Institute of Electronic Structure and Lasers, Heraklion, Greece.
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5
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Vafiadaki E, Arvanitis DA, Pagakis SN, Papalouka V, Sanoudou D, Kontrogianni-Konstantopoulos A, Kranias EG. The anti-apoptotic protein HAX-1 interacts with SERCA2 and regulates its protein levels to promote cell survival. Mol Biol Cell 2008; 20:306-18. [PMID: 18971376 DOI: 10.1091/mbc.e08-06-0587] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Cardiac contractility is regulated through the activity of various key Ca(2+)-handling proteins. The sarco(endo)plasmic reticulum (SR) Ca(2+) transport ATPase (SERCA2a) and its inhibitor phospholamban (PLN) control the uptake of Ca(2+) by SR membranes during relaxation. Recently, the antiapoptotic HS-1-associated protein X-1 (HAX-1) was identified as a binding partner of PLN, and this interaction was postulated to regulate cell apoptosis. In the current study, we determined that HAX-1 can also bind to SERCA2. Deletion mapping analysis demonstrated that amino acid residues 575-594 of SERCA2's nucleotide binding domain are required for its interaction with the C-terminal domain of HAX-1, containing amino acids 203-245. In transiently cotransfected human embryonic kidney 293 cells, recombinant SERCA2 was specifically targeted to the ER, whereas HAX-1 selectively concentrated at mitochondria. On triple transfections with PLN, however, HAX-1 massively translocated to the ER membranes, where it codistributed with PLN and SERCA2. Overexpression of SERCA2 abrogated the protective effects of HAX-1 on cell survival, after hypoxia/reoxygenation or thapsigargin treatment. Importantly, HAX-1 overexpression was associated with down-regulation of SERCA2 expression levels, resulting in significant reduction of apparent ER Ca(2+) levels. These findings suggest that HAX-1 may promote cell survival through modulation of SERCA2 protein levels and thus ER Ca(2+) stores.
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Affiliation(s)
- Elizabeth Vafiadaki
- Molecular Biology Division, Biomedical Research Foundation, Academy of Athens, Greece
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Abstract
It is widely recognized that the accuracy of colocalization measurements is dependent upon the quality of the source images. We demonstrate that, as the image quality increases, the measured colocalization, using the Pearson and Spearman rank correlation coefficients, approaches the true colocalization asymptotically. This means that in practice it is difficult to obtain images of sufficient quality for accurate measurements. We introduce the replicate-based noise corrected correlation (RBNCC) which aligns the measured colocalization with the true colocalization: a noise measurement is made for each fluorophore from a pair of replicate images, the two noise measurements are combined to generate a correction factor which is applied to the measured colocalization between the two fluorophores. In consequence, accurate measurements can be obtained even with noisy images, making RBNCC especially attractive for live imaging. Even with images of apparently good quality we found an average discrepancy of about 20% between the measured and corrected colocalization. A case is made for using the Spearman rank coefficient instead of the Pearson coefficient to measure colocalization.
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Affiliation(s)
- J Adler
- Department Cell Biology, Wenner-Gren Institute, Stockholm University, 106 91 Stockholm, Sweden.
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7
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Coles MC, Veiga-Fernandes H, Foster KE, Norton T, Pagakis SN, Seddon B, Kioussis D. Role of T and NK cells and IL7/IL7r interactions during neonatal maturation of lymph nodes. Proc Natl Acad Sci U S A 2006; 103:13457-62. [PMID: 16938836 PMCID: PMC1569185 DOI: 10.1073/pnas.0604183103] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2006] [Indexed: 12/14/2022] Open
Abstract
Lymph node (LN) development depends on prenatal interactions occurring between LN inducer and LN organizer cells. We have distinguished defects in LN formation due to failure in embryonic development (aly/aly) from defects in postnatal maturation (Il2rgamma(-/-)Rag2(-/-)). Both mutant strains form normal primordial LNs with differing fate. In aly/aly mice, the LN primordium dissipates irreversibly late in gestation; in contrast, Il2rgamma(-/-)Rag2(-/-) LN anlage persists for a week after birth but disperses subsequently, a process reversible by neonatal transfer of WT IL7r(+) TCR(+) T or natural killer (NK) cells, suggesting a role for IL7/IL7r interactions. Thus, we reveal a unique stage of postnatal LN development during which mature lymphocytes and IL7/IL7r interactions may play an important role.
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Affiliation(s)
| | | | | | | | - Stamatis N. Pagakis
- Confocal Microscopy and Image Analysis Laboratory, National Institute for Medical Research, Mill Hill, London NW7 1AA, United Kingdom
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8
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Abstract
Distortions in confocal 3D image data sets were related to movements of the microscope stage that matched fluctuations in laboratory temperature. Movement was apparent in all three axes. Adding a draught-proof enclosure, covering the stage, objective lenses and supporting structures, minimized these short-term fluctuations. However, the stage still tracked slow changes in laboratory temperature and was sensitive to heat sources mounted on the microscope. Suggestions are made about microscope design.
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Affiliation(s)
- J Adler
- Confocal and Image Analysis Laboratory, NIMR, The Ridgeway, Mill Hill, London NW7 1AA, UK
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9
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Ardouin L, Bracke M, Mathiot A, Pagakis SN, Norton T, Hogg N, Tybulewicz VLJ. Vav1 transduces TCR signals required for LFA-1 function and cell polarization at the immunological synapse. Eur J Immunol 2003; 33:790-7. [PMID: 12616499 DOI: 10.1002/eji.200323858] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Activation of T lineage cells through the TCR by peptide-MHC complexes on APC is critically dependent on rearrangement of the actin cytoskeleton. Vav1 is a guanine nucleotide exchange factor for members of the Rho/Rac family of GTPases which is activated following TCR stimulation, suggesting that it may transduce TCR signals to the activation of some or all actin-controlled processes. We show that Vav1-deficient double-positive thymocytes are less efficient at forming conjugates with APC presenting agonist peptide than wild-type cells are. Furthermore we demonstrate that Vav1 is required for TCR-induced activation of the integrin LFA-1, which is likely to explain the defect in conjugate formation. However, once Vav1-deficient cells form a conjugate, the assembly of proteins into an immunological synapse at the conjugate interface is normal. In contrast, thymocyte polarization is defective in the absence of Vav1, as judged by the relocalization of the microtubule-organizing center. These data demonstrate that Vav1 transduces signals to only a subset of cytoskeleton-dependent events at the immunological synapse.
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Affiliation(s)
- Laurence Ardouin
- National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, Great Britain
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Abstract
The Src family tyrosine kinase Lck is essential for T cell development and T cell receptor (TCR) signaling. Lck is post-translationally fatty acylated at its N-terminus conferring membrane targeting and concentration in plasma membrane lipid rafts, which are lipid-based organisational platforms. Confocal fluorescence microscopy shows that Lck colocalizes in rafts with GPI-linked proteins, the adaptor protein LAT and Ras, but not with non-raft membrane proteins including the protein tyrosine phosphatase CD45. The TCR also associates with lipid rafts and its cross-linking causes coaggregation of raft-associated proteins including Lck, but not of CD45. Cross-linking of either the TCR or rafts strongly induces specific tyrosine phosphorylation of the TCR in the rafts. Remarkably, raft patching alone induces signalling events analogous to TCR stimulation, with the same dependence on expression of key TCR signalling molecules. Our results indicate a mechanism whereby TCR engagement promotes aggregation of lipid rafts, which facilitates colocalization of signaling proteins including Lck, LAT, and the TCR, while excluding CD45, thereby potentiating protein tyrosine phosphorylation and downstream signaling. We are currently testing this hypothesis as well as using imaging techniques such as fluorescence resonance energy transfer (FRET) microscopy to study the dynamics of proteins and lipids in lipid rafts in living cells undergoing signaling events. Recent data show that the key phosphoinositide PI(4,5)P2 is concentrated in T cell lipid rafts and that on stimulation of the cells it is rapidly converted to PI(3,4,5)P3 and diacylglycerol within rafts. Thus rafts are hotspots for both protein and lipid signalling pathways.
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Affiliation(s)
- Tony Magee
- Imperial College Faculty of Medicine, London, SW7 2AZ, UK
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Festenstein R, Pagakis SN, Hiragami K, Lyon D, Verreault A, Sekkali B, Kioussis D. Modulation of heterochromatin protein 1 dynamics in primary Mammalian cells. Science 2003; 299:719-21. [PMID: 12560554 DOI: 10.1126/science.1078694] [Citation(s) in RCA: 220] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Heterochromatin protein 1 (HP1beta), a key component of condensed DNA, is strongly implicated in gene silencing and centromeric cohesion. Heterochromatin has been considered a static structure, stabilizing crucial aspects of nuclear organization and prohibiting access to transcription factors. We demonstrate here, by fluorescence recovery after photobleaching, that a green fluorescent protein-HP1beta fusion protein is highly mobile within both the euchromatin and heterochromatin of ex vivo resting murine T cells. Moreover, T cell activation greatly increased this mobility, indicating that such a process may facilitate (hetero)chromatin remodeling and permit access of epigenetic modifiers and transcription factors to the many genes that are consequently derepressed.
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Affiliation(s)
- Richard Festenstein
- CSC Gene Control Mechanisms and Disease Group, Division of Medicine, Imperial College School of Medicine, Hammersmith Campus, Du Cane Road, London W12 ONN, UK.
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12
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Mobasheri A, Golding S, Pagakis SN, Corkey K, Pocock AE, Fermor B, O'BRIEN MJ, Wilkins RJ, Ellory JC, Francis MJ. Expression of cation exchanger NHE and anion exchanger AE isoforms in primary human bone-derived osteoblasts. Cell Biol Int 1999; 22:551-62. [PMID: 10452823 DOI: 10.1006/cbir.1998.0299] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The authors used isoform-specific antibodies against cation (NHE) and anion (AE) exchange isoforms in order to establish their specific expression and localization in dispersed human bone-derived cells. Immunocytochemical preparations of permeabilized osteoblasts probed with polyclonal antibodies were optically analysed by conventional immunofluorescence and con-focal laser scanning microscopy. These techniques demonstrated the abundant presence of epitopes of the cation exchangers NHE1 and NHE3 and the anion exchanger AE2 in these cells. The NHE1 and NHE3 isoform proteins were predominantly located in subplasmalemmal and nucleoplasmic vesicles. The AE2 isoform was densely localized to a subcellular location characteristic of the Golgi complex. The molecular identity of the AE and NHE isoforms was investigated by RT-PCR that confirmed the presence of NHE1 and NHE3 transcripts in addition to NHE4. RT-PCR and diagnostic restriction analysis of amplified AE cDNA established preferential AE2 expression. Since AE2 has been shown to act as a sulfate transporter at low pH, it is possible that it performs this function in the osteoblast Golgi complex where sulfation reactions occur post-translationally on numerous extracellular matrix macromolecules prior to secretion and mineralization. The Na(+)/H(+)exchanger proteins are regulated by mitogenic and non-mitogenic stimuli in the osseus environment and are involved in the large fluxes of ions and protons that necessarily occur during bone formation and resorption and thus play an important role in intracellular ion homeostasis in osteoblasts.
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Affiliation(s)
- A Mobasheri
- Department of Biomedical Sciences, School of Biosciences, University of Westminster, 115 New Cavendish Street, London, W1M 8JS
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Pagakis SN, Curry FE. Imaging of Ca2+ transients in endothelial cells of single perfused capillaries: correlation of peak [Ca2+]i with sites of macromolecule leakage. Microcirculation 1994; 1:213-30. [PMID: 8790591 DOI: 10.3109/10739689409146749] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
OBJECTIVE To investigate the mechanisms responsible for variation in the macromolecular leakage (formation of localized leaky sites) in venular microvessels with increased permeability, we examined the hypothesis that cytoplasmic calcium concentration [Ca2+]i, does not increase uniformly within microvessel endothelial cells. METHODS We loaded the endothelial cells forming the walls of venular microvessels in frog mesentery with fura-2, and imaged [Ca2+]i using a cooled CCD camera. RESULTS Control [Ca2+]i was close to 60 nM in all regions. Control permeability was uniformly low in all microvessels. Exposure to ionomycin (5 mM) increased [Ca2+]i in a biphasic manner, but not uniformly. There was variation in both time to peak (bimodal distribution) and peak [Ca2+]i (274 +/- 13 nM; mean variation above or below the peak value was 110 nM). Raising extracellular calcium from 1.1 to 5 mM increased the mean variation of [Ca2+]i about peak values. Extravascular leakage of fluorescently labeled albumin or low-density lipoproteins was most prominent at sites where increase in [Ca2+]i were largest. CONCLUSIONS These data indicate that variation in [Ca2+]i within individual endothelial cells or groups of cells could account, at least in part, for the distribution of localized leakage sites for macromolecules in venular microvessels in the high-permeability state.
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Affiliation(s)
- S N Pagakis
- Department of Human Physiology, School of Medicine, University of California, Davis 95616, USA
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14
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Abstract
Previous studies from this laboratory indicated that in the early phase of a high-permeability state, low-density lipoprotein (LDL) crosses the microvascular barrier by porous pathways. To determine the extravascular distribution of LDL (3,500,000 MW) and a smaller reference macromolecule [20,000 MW dextran (D20)] image processing techniques were employed, and extravascular accumulation of solutes from different microvessels was compared to quantitative fluorescence microscopy. Frog mesenteric venular microvessels (n = 8) were cannulated and perfused with fluorescent-labeled LDL and D20 and extravascular distribution of both solutes was imaged at control and after permeability was increased with the calcium ionophore ionomycin (5 microM). At the peak increase in apparent permeability (2-4 min after ionophore), the processed images of the microvessels demonstrated that the extravascular distribution of fluorescent-labeled solute was not uniform and that D20 accumulated outside the microvessel wall in some areas where LDL did not accumulate. The patterns of extravascular accumulation of LDL and D20 in a high-permeability state imply a distribution of effective microvascular pore sizes and/or a distribution of resistances to solute flow in the pore or in the tissue surrounding the microvessel.
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Affiliation(s)
- J C Rutledge
- Division of Cardiovascular Medicine, University of California, Davis 95616
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15
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Abstract
We investigated the hypothesis that an increase in cytoplasmic calcium ion concentration, [Ca2+]i, is one of the mechanisms responsible for increased microvessel permeability. We loaded the cells forming the walls of individually perfused microvessels in frog mesentery with fura-2 and measured [Ca2+]i in the control state and after adding the Ca2+ ionophore ionomycin to the perfusate. [Ca2+]i in the control state was 65 +/- 6 nM and increased to an initial peak of 285 +/- 29 nM after 1-3 min. After 4, 6, and 10 min, [Ca2+]i was 199 +/- 18, 163 +/- 16, and 129 +/- 9 nM, respectively. [Ca2+]i fell back to 77 +/- 7 nM after ionophore was removed. In similar experiments, hydraulic conductivity (Lp) increased to a peak of 9.5 times control after 1-3 min, then fell to 2.0 times control after 6 min. Lp remained elevated at this level for as long as ionophore was present in the perfusate. [Ca2+]i modulates the initial and sustained phases of the permeability increase. Both processes depend on external Ca2+ influx. Our experiments provide the first direct measurement of [Ca2+]i during a change in the permeability of an intact microvessel.
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Affiliation(s)
- P He
- Department of Human Physiology, School of Medicine, University of California, Davis 95616
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